Construction or agricultural equipment is frequently stored out of doors, and to prevent rain, snow and other materials from entering the vertical exhaust pipe during periods of non-operation, protective caps are frequently used in conjunction with the exhaust pipe. The typical protective cap is hinged to the upper end of the exhaust pipe and is counterweighted to the closed position. On operation of the engine, the increase of pressure in the exhaust pipe will move the cap to the open position.
The conventional pressure responsive cap is subject to vibration due to surges of pressure within the exhaust pipe, and the vibration not only generates substantial noise, but produces fatigue on the components of the cap, with the result that the cap has a limited life of service.